Cell culture of mammalian cells has long been used for the production of many vaccines and genetically engineered proteins. Attachment-dependent cells have historically been cultivated on the walls of roller bottles or non-agitated vessels such as tissue culture flasks, which are used in many laboratories. As the need has developed to provide large amounts of certain antiviral vaccines, genetically engineered proteins, and other cell-derived products, attempts have been made to develop new systems for large-scale production of cells. One solution has been to increase the growth surface area per unit vessel volume and to implement convenient and appropriate environmental controls. Some of these technologies involved the use of packed-glass beads, stacked plates, rotating multiple tubes, and roller bottles with spiral films inside.
Using microcarriers for cell culture increases the surface area of growth by allowing cells to grow as monolayers on the surface of small spheres or other globular micro-structures, or as multilayers in the pores of macroporous structures. First described in 1967 by van Wezel (van Wezel, A. L. “Growth of Cell-Strains and Primary Cells on Micro-carders in Homogeneous Culture” (1967) Nature 216:64-65), early microcarriers consisted of positively charged DEAE-dextran beads suspended in culture media in a stirred vessel. Cells would attach to the bead surface and grow as a monolayer.
Various other materials have been used for microcarriers and microcarrier and cell culture substrate coatings since van Wezel's DEAE-dextran beads (see, e.g., review in van der Velden-de Groot, Cytotechnology (1995) 18:51-56). However, new materials are needed in order to provide optimal cell culture conditions for various applications. Additionally, biocompatible microcarriers are needed that may be used directly in methods of treatment, without the need for cell harvesting.
The ability of complex substrates to support cell growth in vitro has been reported, and matrix products supporting such growth are commercially available. For example, there is Human Extracellular Matrix and BD Matrigel™ Basement Membrane Matrix (BD Biosciences). Human Extracellular Matrix is a chromatographically partially purified matrix extract derived from human placenta and comprises laminin, collagen IV, and heparin sulfate proteoglycan. (See U.S. Pat. No. 4,829,000 to Kleinman et al.). BD Matrigel™ is a soluble basement membrane extract of the Engelbreth-Holm-Swarm (EHS) tumor, gelled to form a reconstituted basement membrane. Both of these matrix products require costly biochemical isolation, purification, and synthesis techniques and thus production costs are high.
Therefore, alternative compositions are needed which can support cell growth in vitro. Alternative materials with improved characteristics and/or lower cost would be beneficial.